The invention relates to a low-pressure discharge lamp comprising
a tubular glass lamp vessel which is closed in a vacuumtight manner and has end portions; PA1 a cylindrically curved metal body to which an end portion of the lamp vessel is fused and which has an exposed outer surface outside the lamp vessel; PA1 an ionizable filling comprising rare gas in the lamp vessel.
The invention also relates to a luminaire provided with such a lamp.
Such a low-pressure mercury discharge lamp, which is a mercury vapour fluorescent lamp, is known from U.S. Pat. No. 2,433,218.
In the known lamp, the two end portions of the lamp vessel are fused to a metal bush which has its bottom outside the lamp vessel. The moment the lamp vessel is fused to the bushes, the lamp vessel is closed in a vacuumtight manner. Impurities must have been removed from the lamp vessel at that moment and the desired gas filling must be present therein. Cleaning of the lamp vessel, providing the gas filling and at the same time keeping the relevant bush in position relative to the lamp vessel during fusion thereof are difficult and require complicated equipment. The degree of difficulty of the lamp manufacture is higher in proportion as the lamp vessel is longer and/or narrower.
The cylindrically curved metal body of the known lamp has a complicated shape and has portions which are narrowed relative to the portion to which the lamp vessel is fused, both inside and outside the lamp vessel. The internal narrowed portion functions as a hollow electrode during operation. Alternative bodies are assembled from various pans, for example, a cup-shaped pan and a cylinder on the bottom thereof.